Official Discussion issued by the National Hurricane Center
IGOR (AL112010) DATA RELEASED: 9/8/2010 11:00:00 AM UTC
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Copy of official data TROPICAL STORM IGOR DISCUSSION NUMBER 1 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112010 1100 AM AST WED SEP 08 2010 THE LOW OVER THE FAR EASTERN TROPICAL ATLANTIC OCEAN HAS BECOME BETTER DEFINED AND DEEP CONVECTION NEAR THE CENTER HAS PERSISTED LONG ENOUGH FOR THIS SYSTEM TO BE CONSIDERED A TROPICAL CYCLONE. A 1042 UTC ASCAT PASS SHOWED WINDS OF 35 KT...AND THE INITIAL INTENSITY WILL BE SET TO THAT VALUE. EASTERLY SHEAR IS PRESENT OVER IGOR...BUT IS FORECAST TO LIGHTEN IN A DAY OR SO. ALL RELIABLE MODELS SHOW INTENSIFICATION INTO A HURRICANE IN THE NEXT SEVERAL DAYS. BECAUSE OF THE SHEAR...THE NHC INTENSITY FORECAST WILL ONLY SHOW RELATIVELY SLOW STRENGTHENING...BELOW THE GUIDANCE INITIALLY...BUT THE FORECAST ENDS UP CLOSE TO THE CONSENSUS AT DAY 5. IF THE UPPER ANTICYCLONE PATTERN SEEN IN MOST OF THE GLOBAL MODELS VERIFY...THE OFFICIAL FORECAST COULD BE CONSERVATIVE IN THE LATTER PART OF THE FORECAST PERIOD. THE INITIAL MOTION IS 265/7. A MID-LEVEL RIDGE OVER THE EASTERN ATLANTIC OCEAN IS FORECAST TO STRENGTHEN OVER THE NEXT FEW DAYS...WHICH SHOULD CAUSE A WESTWARD MOTION AT AN INCREASING FORWARD SPEED. AT THE END OF THE PERIOD...A TROUGH OVER THE CENTRAL ATLANTIC COULD WEAKEN THE RIDGE...FORCING THE STORM TO MOVE MORE TO THE WEST-NORTHWEST. THE MODEL GUIDANCE IS IN RELATIVELY GOOD AGREEMENT ON THIS SCENARIO...ALTHOUGH THERE IS SOME SHORT-TERM UNCERTAINTY ON HOW IGOR WILL INTERACT WITH THE LARGE CONVECTIVE SYSTEM TO THE NORTHEAST OF THE STORM. THE NHC FORECAST IS NEAR OR SLIGHTLY SOUTH OF THE MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 08/1500Z 13.7N 23.5W 35 KT 12HR VT 09/0000Z 13.7N 24.6W 40 KT 24HR VT 09/1200Z 13.8N 26.6W 45 KT 36HR VT 10/0000Z 14.0N 29.0W 50 KT 48HR VT 10/1200Z 14.5N 31.5W 55 KT 72HR VT 11/1200Z 15.5N 3 |